Generally, one of the numerous ways of categorizing photoflash lamps is those which are electrically activated and those which are percussively activated. Ordinarily, the electrically activated photoflash lamps are of the filamentary type wherein a pair of electrically conductive leads are sealed in a glass envelope with a filament wire interconnecting the electrically conductive leads within the envelope. A primer material is applied to one or both of the conductive leads within the envelope and contiguous with the filament wire. In operation, a relatively low voltage high current source, as for example a voltage of 10.0-volts or less and a current of several hundred milliamperes, is coupled to the electrically conductive leads external to the envelope. This potential source causes the filament wire, usually tungsten, to melt and ignite the primer material affixed to the leads and, in turn, expels burning particles into a shredded fill within the envelope which produces the actinic output of the flashlamp.
On the other hand, the percussively activated flashlamp includes an anvil which is in contact with a primer material especially responsive to any movement thereof to provide burning particles suitable for igniting the shredded fill within the envelope. In operation, a striker activates the anvil which, in turn, causes movement of the primer material in an amount sufficient to cause expulsion of burning particles and ignition of the shredded fill.
Additionally, electrically-activated flashlamps are available wherein a pair of electrically conductive leads are embedded in a glass envelope and a primer material is disposed immediately adjacent one or more of the conductive leads interiorly of the envelope. In operation, a relatively high voltage, anywhere from several hundred to a thousand or more volts at very low currents, is applied to the conductive leads and, in turn, to the primer material. Thereupon, the primer material is activated and ignites the shredded fill within the envelope.
In the past, it was not uncommon to utilize a camera providing a relatively low voltage output in conjunction with a filament-type flashlamp. In such combinations it was also not uncommon to employ a so-called "M-Sync" type operation wherein power was applied to the flashlamp prior to the activation of the camera shutter. As a result, there was sufficient time for the flashlamp to provide the desired actinic output during the period of shutter activation. In other words, activation of the flashlamps 15 to 20 msecs. prior to activation of the camera shutter compensated for the relatively slow reaction of the flashlamp as compared with the activation of the camera shutter.
However, recent advances in films and cameras have resulted in the so-called "X-Sync" type operation wherein activation of the flashlamp and the camera shutter occurs substantially simultaneously. As a result, it was found that difficulties were encountered when utilizing a filament-type flashlamp with an "X-Sync" type camera having a relatively low voltage source.
More specifically, it has been found that the dark time or the time between energization of the filament and the initiation of actinic output from the flashlamp is a problem when presently known low voltage filament-type flashlamps are utilized with an "X-Sync" type camera. Since the filament does not begin to melt or burn immediately upon application of current but rather gradually heats and then burns and the fact that the primer material is not activated until the filament melts and reaches the primer material causing expulsion of burning particles toward the shredded fill material, the resultant appearance of the actinic output of the flashlamp is unduly delayed as compared with the camera shutter speed. As a result, the camera shutter could be operational prior to the provision of a maximum actinic output from the flashlamp.
Actual measurements of available filament-type flashlamps indicated a dark time in the range of about 3.0 to 3.5 msecs. However, it has been found that a reduction in this dark time period, and consequently, a more rapid appearance of the peak light output of the filament-type flashlamp, would be advantageous when an "X-synchronized" camera is employed.